A160995 The smallest positive integer neither a divisor of n nor coprime to n.

4, 6, 6, 10, 4, 14, 6, 6, 4, 22, 8, 26, 4, 6, 6, 34, 4, 38, 6, 6, 4, 46, 9, 10, 4, 6, 6, 58, 4, 62, 6, 6, 4, 10, 8, 74, 4, 6, 6, 82, 4, 86, 6, 6, 4, 94, 9, 14, 4, 6, 6, 106, 4, 10, 6, 6, 4, 118, 8, 122, 4, 6, 6, 10, 4, 134, 6, 6, 4, 142, 10, 146, 4, 6, 6, 14, 4, 158, 6, 6, 4, 166, 8, 10, 4, 6

Offset

2,1

Comments

a(1) doesn't exist because 1 is coprime to all integers.

Links

Charles R Greathouse IV, Table of n, a(n) for n = 2..10000

Formula

a(p) = 2p, for all primes p.

Prog

(PARI) a(n)=for(k=4, 2*n, if(gcd(n, k)>1 && n%k, return(k))) \\ Charles R Greathouse IV, Apr 05 2013
(PARI) a(n)=my(f=factor(n), b); forprime(p=2, , if(n%p, b=p*f[1, 1]; break)); for(i=1, #f[, 1], b=min(b, f[i, 1]^(f[i, 2]+1))); b \\ Charles R Greathouse IV, Apr 05 2013

Crossrefs

Sequence in context: A199172 A323674 A183986 * A215454 A155750 A159475

Adjacent sequences: A160992 A160993 A160994 * A160996 A160997 A160998

Keyword

nonn

Author

Leroy Quet, Jun 01 2009

Extensions

Extended by Ray Chandler, Jun 13 2009

Status

approved